1. Field of the Invention
The present invention relates to a stimulator circuit, particularly to a bioelectric current stimulator circuit.
2. Description of the Related Art
The conventional bioelectric current stimulators may be categorized into two types. One type is disposed outside human bodies, and the other type is disposed inside human bodies, functioning as the auxiliary devices of sensory organs. One example of the former is a Taiwan patent No. I306407 “Device and Method for Generating Biomedical Electronic Signals”. Examples of the latter include a U.S. Pat. No. 6,289,246 “High Compliance Output Stage for a Tissue Stimulator” and a U.S. Pat. No. 5,350,407 “Implantable Stimulator Having Quiescent and Active Modes of Operation”.
In applications of the abovementioned stimulators to auxiliary devices of sensor organs, the load impedance ranges from tens of kΩ to hundreds of kΩ, depending on the contact points on the human or animal body. Even in the same contact point, the load impedance may also vary with the duration of contacting and the material of electrodes. Thus, the conventional stimulators cannot effectively output stimulus current when the load impedance is mismatched.